Miscellaneous Communication Circuits

The ABS/TCS communicates with the Body Computer Module (BCM) for the purpose of displaying failure messages and diagnostic trouble codes. Communication occurs on six circuits; failures in the ABS/TCS may result in up to three BCM trouble codes and/or four Driver Information Center Messages.

Low Brake Fluid
The Low Brake Fluid line (circuit 853, between the fluid level sensor, EBCM pin 34 and BCM pin 3D1) is held at 12 volts by both the BCM and the EBCM. Any time that this circuit is grounded by the fluid level sensor, the following action takes place:

^ The EBCM disables antilock and traction control modes, grounds the ABS/TCS Fault Line and grounds the BRAKE lamp circuit.
^ The BCM enables the LOW BRAKE FLUID message and turns on the BRAKE warning lamp in the Instrument Panel Cluster (IPC). In response to the EBCM grounding the ABS/TCS Fault line, the BCM will also enable the ANTILOCK DISABLED and TRACTION DISABLED messages.

The ANTILOCK DISABLED message has a higher priority than the LOW BRAKE FLUID message; as a result, the LOW BRAKE FLUID message will be seen only at key-on.

Diagnostic Enable
ABS/TCS diagnostic trouble code display is enabled any time the Diagnostic Enable line is held to ground. ABS/TCS diagnostics are requested by grounding Assembly Line Data Link (ALDL) pin H; the EBCM will blink diagnostic codes.

Traction Disable - Mini-Spare
The mini-spare connector in the trunk must be disconnected any time the spare tire is in use. When it is disconnected a 12 volt signal is sent to the BCM (BCM pin 2B3). When this signal is received by the BCM, it will turn on the TRACTION DISABLED FOR MINI-SPARE message.